The invention described herein was made in the course of work under a grant or award from the Department of Health and Human Services.
The invention relates to immunoassaying for, and purification of, proteins--e.g., erythropoietin, a hormone involved in regulation of red blood cell development.
Protein immunoassays are useful, e.g., to diagnose human disease states. Abnormal levels of erythropoietin, for example, may signify many forms of anemia, certain heart and lung diseases, tumors, renal failure, and other diseases. Purified proteins and antibodies thereto are used to treat various disease states. For example, purified erythropoietin may be used to treat anemia associated with renal failure.
In protein immunoassays, a sample having an unknown concentration of the protein is mixed with a known concentration of the protein which has been labeled to form a tracer compound. The tracer and sample protein compete to bind to an antibody which has been raised to the protein. The extent to which the labeled protein binds to the antibody can be measured (either by measuring the bound or the unbound tracer) and will be inversely affected by the protein concentration in the sample, according to known relationships which may be used to derive that concentration. Thus, in the conventional immunoassay, the protein being assayed serves both as the antigen used to raise the antibody and as the labeled tracer used to determine the sample protein concentration.
Li U.S. Pat. No. 4,096,237 discloses such an immunoassay for a human protein hormone known as .beta.-endorphin, using radioactively labeled .beta.-endorphin as a tracer and antibodies raised to .beta.-endorphin. Li also discloses that the above tracer and antibodies may be used to assay a related protein, such as camel .beta.-endorphin or a specific peptide fragment thereof which "exhibited a parallel inhibition curve, but had 40% immunoreactivity as compared to the full sequence of camel .beta.-endorphin" (2:18-20).